Physical protection of C and greenhouse gas emissions provided by soil macroaggregates from a Chilean cultivated volcanic soil
2012
Muñoz, Cristina | Torres, Pablo | Alvear, Marysol | Zagal, Erick
Soils can act as either sinks or source of greenhouse gas (GHG) depending on how flows are affected by management practices, but limited information is available on volcanic soils. This study aimed to examine the physical protection of C and GHG emissions provided by soil macroaggregates in a cultivated volcanic soil under no-till soil management and different N source fertilization and liming additions. A long-term experiment under no-till system was used. Studied plots had been fertilized annually from 1996 to the present with four fertilization treatments: nitrate (T1), ammonium (T2), ammonium plus 0.5 Mg CaCO₃ ha⁻¹ (T3), and ammonium plus 1 Mg CaCO₃ ha⁻¹ (T4). Soil samples were collected in 2009. From each treatment, six sizes of soil macroaggregates were obtained by dry sieving (0.25–0.5 mm, 0.5–1 mm, 1–2 mm, 2–4 mm, 4–6 mm, >6 mm in diameter): one subsample was kept undisturbed and another subsample was finely crushed. Microbial biomass and CO₂ and N₂O emissions were evaluated through soil aerobic incubations in laboratory. There was a trend of smaller macroaggregate that showed higher CO₂ emissions in T1 and T3, and higher N₂O emissions were observed in T1, T2, and T3. It was concluded that soil macroaggregates larger than 2 mm produce less CO₂ and N₂O than smaller ones in a no-till systems. The physical protection exerted by soil macroaggregates on soil organic C was confirmed.
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